1. Field of the Invention
This invention relates to glass structures having an infrared reflective coating of conductive tin oxide thereon, and, more particularly, to non-iridescent, transparent, haze-free, low emissivity, infrared-reflecting, energy efficient glass window structures which are provided with an iridescent-masking coating of tin oxide which is transparent and haze-free.
2. Description of the Prior Art
The art recognizes that glass and other transparent materials can be coated with transparent conductive tin oxide films in order to reflect infrared radiation. Such structures are useful in providing windows with enhanced insulating value, i.e. lower heat transport.
Tin oxide films are especially effective infrared reflectors at thicknesses of about 1000 to 8000 Angstroms. However, at such thicknesses the films tend to display interference effects, i.e., multiple visible colors, commonly referred to as iridescence. These interference effects render the coated glass aesthetically unacceptable for most architectural applications. Iridescence is not observed in thinner films: however, these films have insufficient infrared reflectance to be of practical utility. Likewise, iridescence is not observed in thicker films but such films tend to be hazy, and absorb considerable light and are difficult to make uniformly. Therefore, various methods to mask interference effects have been developed.
Particularly, the objectionable interference colors (iridescence) in reflected light has been diminished by the structures provided by Gordon, in U.S. Pat. Nos. 4,187,336; 4,206,252; 4,308,316 and 4,377,613; and by Michelotti and Henery in EPO No. 0137,161, published Apr. 17, 1985. These infrared reflecting coated glass structures include means designed to diminish the iridescence effect. However, while these coatings function effectively for the purpose of reducing iridescene, they introduce haze into the system unless formed under very restrictive and disadvantageous deposition conditions. Gordon, for example, states that haze, which ordinarily would appear in the tin oxide coating, can be reduced by first depositing on the window glass an amorphous layer of SiO.sub.2, Si.sub.3 N.sub.4, GeO.sub.2, Al.sub.2 O.sub.3, or silicon oxy-nitride, or mixtures thereof with each other, or with other metal oxides. However, Gordon cautions that if this layer contains a large proportion of the metal oxides, Ga.sub.2 O.sub.3, ZnO, In.sub.2 O.sub.3, or SnO.sub.2, then haze formation is likely.
In the art, it is recognized that the appearance of haze in tin oxide coatings formed on glass by exposure to tin compounds can be prevented or reduced by application of an intervening coating of suitably selected composition. For example, U.S. Pat. No. 2,617,741 proposes to provide a protective layer preceding the formation of the tin oxide coating by spraying the heated glass with a saturated or relatively concentrated aqueous solution of a suitable soluble metal salt, particularly the acetates of copper, aluminum, lead, zinc, iron, nickel, cobalt, thallium, silver or titanium.
Similarly, Terneu in U.S. Pat. No. 4,329,379, describes an undercoat of a metal oxide formed by decomposition of the acetylacetonate of titanium, nickel or zinc on which a tin oxide overcoat free from perceptible haze can be formed.
Two-layered, haze-free glass structures also are described in U.S. Pat. Nos. 4,547,400 and 4,548,836. The patents state that the undercoat should be made from a chlorine-free organotin compound, particularly dibutyltin diacetate.
Accordingly, it is an object of this invention to provide transparent, non-iridescent, haze-free, energy efficient glass structures which includes a first conductive tin oxide coating which reflects infrared radiation, and a second, haze-free tin oxide coating, which reduces iridescence in said structure.
Another object of the invention is to provide such transparent, non-iridescent, haze-free energy efficient glass structures having a plurality of tin oxide coatings including a transparent, conductive tin oxide coating which reflects infrared radiation and a haze-free tin oxide coating which reduces iridescence, made by chemical vapor deposition of monophenyltin trichloride.
Still another object herein is to provide transparent, non-iridescent, haze-free, infrared reflecting glass window structures which includes a transparent, haze-free tin oxide coating made from monophenyltin trichloride on one surface of a glass sheet and a second, transparent, conductive tin oxide coating on the opposite surface of said sheet, in predetermined thicknesses relative to each other to substantially reduce iridescence in said structure.
A further object of this invention is to provide a non-iridescent, haze-free tin oxide coating energy efficient, glass window structure capable of reflecting infrared energy which includes a transparent, haze-free tin oxide coating composed of two layers including an undercoat layer close to the glass made by depositing monophenyltin trichloride in air, and an overcoat layer of tin oxide which assumes the haze-free characteristics of the undercoat layer.
Among the other objects of the invention is to provide an energy efficient, double-glazed glass window structure which is non-iridescent, and in which the haze-free tin oxide coating which is present for the purpose of reducing iridescence is made by chemical vapor deposition of monophenyltin trichloride.